Screw-rotor machine

ABSTRACT

A rotary screw-type machine in which the inlet port is made in the casing at one end face of the rotary screws while the outlet port is made in the casing at the other end face of these rotary screws, in which case the sections of the port contours follow the arc of the addendum and dedendum circles of the teeth of the screws and the profiles of the teeth, while at the zone of contact of the teeth of the screws they follow the line of engagement of these teeth.

United States atem Inventors Appl. No. Filed Patented Alexandr Ivanovich Borisoglebsky Drezdenskaya, ulitsa, 42, kv. 74;

Boris Lazarevich Grinpress, Tikhoretsky prospekt, 20, kv. 20; Ivan Akimovich Sakun, Krasnoputilovskaya ulitsa, 12, kv. 44; Jury losifovich Dlmentov, Budapeshtskaya ulltsa, 38, korpus 2 kv. 89; Valentin Nlkolaevlch Pyankov, Lenlngradskol oblastl, ulitsa Leningtadskaya, 61. kv. 51; Moisel Fishelevich Vainshtein, Nevsky prospekt, 27, kv. 15; Rafkhat Izmailovich Khasanov, prospekt Engelsa. 73, kv. 2, allot Leningrad, U.S.S.R.

Oct. 14, 1969 Nov. 23, 1971 SCREW-ROTOR MACHINE 3 Claims, 4 Drawing Figs.

U.S.C1

Int. Cl

................................................ F0lc 1/16,

F04c 1/10, F04c 17/12 [50] Field of Search 418/201; 91/84; 123/12 BC [56] References Cited UNITED STATES PATENTS 2,474.653 6/1949 Boestad 418/201 2,531,603 11/1950 Berck.. 91/84 2,547,169 4/1951 Paget 418/201 2,705,922 4/1955 Rathman... 418/201 2,804,260 8/1957 Nilsson et a1. 418/201 3,108,740 10/1963 Schibbye 418/201 Primary ExaminerCarlton R. Croyle Assistant Examiner.1ohn .1. Vrablik AImrneyWaters, Roditi, Schwartz & Nissen ABSTRACT: A rotary screw-type machine in which the inlet port is made in the casing at one end face of the rotary screws while the outlet port is made in the casing at the other end face of these rotary screws, in which case the sections of the port contours follow the arc of the addendum and dedendum circles of the teeth of the screws and the profiles of the teeth, while at the zone of contact of the teeth of the screws they fol low the line of engagement of these teeth.

PATENTEB NOV 2 3 19m SHEET 2 OF 3 PATENTEUNUV 23 l97| SHEET 3 BF 3 SCREW-ROTOR MACHINE The present invention relates to rotary screw-type machines with male and female rotary screws having intermeshing threads. Provided between the teeth of the rotary screws and the casing of the machine are chambers for charging therein a gaseous medium. If a torque is applied to one of the rotary screws they start to rotate. and the machine compresses the said medium like a compressor.

If the gaseous medium is supplied under pressure into the above-mentioned chambers, the rotary screws begin to rotate and in this case the machine can be utilized as a motor.

The present invention can be most effectively used in case when the profile of each tooth of the male rotary screw is along an elliptical, cycloidal or any other curve whose shape is similar to that of said curves, while the profile of each tooth of the female rotary screw is along a curve enveloping the curves formed by the points of the profile of the male rotary screw tooth during the rotation (such a profile is described in the USSR lnventors Certificate No. 1244860, class 27c 3/0l, 1960).

The rotary screw-type machines, known in the prior art are provided with two parts for admitting and exhausting the gaseous medium, one of these ports being usually located on the low-pressure side in the lower portion of the casing. The port opening is positioned opposite to the teeth of the male and female rotary screws, the contour of the port following the arcs of the addendum and dedendum circles of the teeth. The lateral sides of the port repeat the profile of the teeth against which they are disposed, while the contour the median portion of the port at the teeth meshing zone follows the profile of the tooth of the male rotary screw.

The other port is usually positioned at the high-pressure side in the upper portion of the casing and differs from the former in that its opening has a smaller length, whereas, the part of the port disposed on the cylindrical portion of the casing features a triangular shape (for example, see the book by I. A. Sakun "Screw-type Compressors, Moscow-Leningrad, I960, pages 13-35).

The operation of the known screw-rotor machines is associated with some difficulties due to the fact that a gap is formed between the contacting teeth of the male and female rotary screws through which the low-pressure zone communicates with the high-pressure zone, because during the rotation of the screws a portion of the gap is near the opening of the inlet port at one face side of the screws while the other portion of the gap is at the other face side of the rotary screws near the opening of the outlet port. THis results in excessive energy losses.

An object of the present invention is to eliminate the abovementioned disadvantages.

The principal object of the invention is to provide such a rotary screw-type machine in which the contours of the inlet and outlet ports are such that the gap formed between the contacting teeth of the screws would not communicate with the openings of said ports.

According to the invention, this object is achieved due to the fact that the sections of the contours of both the inlet and outlet ports at the zone of contact of the teeth of the male and female screws follow the line of engagement of these teeth.

In this case, in order to make the port opening as large as possible, it is expedient that the contour section of the port following the line of engagement of the teeth is smoothly conjugated with the contour section following the arc of the addendum circle of the teeth of the male screw.

In one embodiment of the invention the contour section following the line ofengagement of the teeth is expediently made adjacent to the section following the arc of the addendum circle of the female screw on the side of the male screw.

In the port located on the high-pressure side of the rotary screw machine of the liquid-injection type the contour section of this port following the line of engagement of the teeth is expedient by made adjacent to the section following the arc of the circle circumscribed by the radius equal to the height of the tooth of this screw on the side of the male screw. In this case the next section on the side of the above screw must follow the arc of the addendum circle of the female screws.

Such a formation of the port makes it possible to increase its opening without increasing the volumetric losses due to the fact, that the gap between the contacting teeth at the beginning of the line of engagement is small and is filled with the injected liquid.

An essential advantage of the present invention consists in that the volumetric losses of the rotary screw-type machine are reduced approximately by 15-20 percent.

Given below is a detailed description of preferable embodiments of the present invention with reference to the accompanying drawings, in which:

FIG. I shows a longitudinal section of the rotary screw-type machine according to the invention;

FIG. 2 shows a section, taken along the line "-11 of FIG. I;

FIG. 3 shows a section taken along the line III-III of FIG. I, the first embodiment of the outlet port;

FIG. 4 shows the second embodiment of the outlet port.

A rotary screw-type machine, utilized for example as a compressor, has a male rotary screw I (FIGS I, 2) in which the profile of each tooth 2 is along an elliptical curve. The male screw I meshes with a female screw 3 in which the profile of each tooth 4 follows the curve enveloping the curves formed by the points of the profile of the tooth 2 of the male screw I during its rotation. The screws I and 3 are mounted in a casing 5 having an inlet branch 6 and an outlet branch 7. The branch 6 communicates with the chambers formed by the teeth of the screws and by the casing through an outlet port 8 (FIG. 2). The contour of the port 8 represents a closed line A B C D E F G H K L A whose sections are made as follows. The section AB and the section CD are accomplished along the arc of the addendum circle of the teeth 4 of the female screw 3 and along the arc of the addendum circle of the teeth 2 of the male screw I. The sections AB and CD are connected by the linear section BC which is a tangent to said circles.

The section DE follows the profile of the tooth 2 of the male screw I. THe section EF follows the arc of the dedendum circle of the teeth 2 of the male screw I. The section GH follows the arc of the addendum circle of the teeth 4 of the female screw 3. The sections EF and HG are conjugated by means of the arc GF which reduces the stresses and hydraulic losses.

At the zone of contact of the teeth 2 and 4 of the screws I and 2 the contour of the port 8 has a curvilinear section HK following the line of engagement of said teeth. The section HK is followed by the section KL along the arc of the dedendum circle of the teeth 4. The sections KL and BA are connected by a section LA following the profile of the tooth 4.

FIG. 2 shows such a position of the screws I and 3 in which the point of contact of the tooth 2 with the tooth 4 approaches the point H along the curve KH (the directions of rotation of the screws are indicated by arrows).

It is clear that the contact of the teeth 2 and 4 starts at the point K. Therefore, the gap between the contacting teeth 2 and 4 is beyond the opening of the port 8, i.e. is either above the line HK or coincides with it. In this case the low-pressure zone does not communicate with the high-pressure zone through said gap. The volumetric losses of the machine are thus considerably reduced.

The outlet port 9 (FIG. 3) is made essentially in the same manner as the inlet port 8. The contour of the port 9 is essentially a closed line M N N O P Q R S T M in which the sections MN and OR follow the arc of the addendum circle of the teeth 4 of the screws 3, while the sections OP and TS follow the arcs of the dedendum circles of the teeth 2 and 4 respectively. The section MN the arc of the addendum circle of the teeth 2. The sections ON and TM follow the profiles of the teeth 2 and 4 respectively. The section PQ is along the arc of the circle, taking into account the considerations on the basis of which the section GF in FIG. 2 was formed. The section RS is along the line of engagement of the teeth 2 and 4. The section RS prevents the machine high-pressure zone from communicating with the low-pressure zone, which also causes the reduction of the machine volumetric losses.

The second embodiment of the outlet port 90 (FIG. 4) is intended for the liquid-injection machine. The contour of this port represents a closed line M N O P Q R R STM in which the sections TM, OP, PO and TS are made similarly to the same sections in FIG. 3. The section MN" follows the arc of the addendum circle of the teeth 4 of the female screw 3, how ever, a part of this section is within the addendum circle 2 of the male screw l. The section N"O follows the profile of the tooth 2 of the male screw I. The section QR follows the arc of the addendum circle of the teeth 4 of the female screw 3. The section SR" follows the line of engagement of the contacting teeth 2 and 4. Provided between the sections SR" and R'Q is a section RR following the arc circumscribed by the radius R.

The length of this radius is equal to the height of the tooth 2 of the male screw 1.

Thus, the opening of the port 9 is increased within the zone of contact of the teeth 2 and 4 due to the fact that the section P"P' is nearer to the plane matched with the axes of rotation of the screws l and 3 than the section R"R of the line of engagement SR indicated by the dotted lines.

What we claim is:

l. A rotary screw type machine comprising a casing with inlet and outlet pipe-unions for a gaseous medium, intermeshing, rotatable male and female screws mounted within said casing, said male screw having a tooth with an elliptical profile, and said female screw having a tooth with a profile which is the envelope of the curve formed by rotation of the tooth of the male screw, said casing having an inlet port at one face of said screws and an outlet port at the other face of said screws, the contour of both inlet and outlet ports following the arcs of the addendum and dedendum circles of the teeth of said screws and following the profiles of those of said teeth, which are located opposite to the sections of said contour, in which case the section of said contour at the zone of contact of said teeth is made along the line of engagement of these teeth thereby preventing direct communication between said ports.

2. A rotary screw-type machine according to claim I in which said section of said contour following said line of engagement of said teeth is adjacent to a section following the arc of the addendum circle of the teeth of said female screw on the side of said male screw.

3. A rotary screw-type machine according to claim I in which one of said ports located at the high-pressure side has a contour following the line of engagement of said teeth and having a section which on the side of said male screw adjoins the section following the arc of the circle circumscribed by the radius equal to the height of the tooth of said male screw, in which case the next section of said contour on the side of said male screw is along the arc of the addendum circle of the teeth of said female screw.

i i i t UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,622 .256 Dated November 23. 1.971

lnventofls) Alexandr Ivanovich Borisgoglebsky et a1 It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line 19: 112M860 to This certificate supersedes Certificate of Correction issued June 26, 1973,-

Signed and sealed this 31st day of December 1974.

(SEAL) Attest:

McCOY M. GIBSON JR. C. I IARSHALL DANN Arresting Officer Commissioner of Patents UiS GOVERNMENT PRINTING OFFICE 1.. 0-355-33, 

1. A rotary screw type machine comprising a casing with inlet and outlet pipe-unions for a gaseous medium, intermeshing, rotatable male and female screws mounted within said casing, said male screw having a tooth with an elliptical profile, and said female screw having a tooth with a profile which is the envelope of the curve formed by rotation of the tooth of the malE screw, said casing having an inlet port at one face of said screws and an outlet port at the other face of said screws, the contour of both inlet and outlet ports following the arcs of the addendum and dedendum circles of the teeth of said screws and following the profiles of those of said teeth, which are located opposite to the sections of said contour, in which case the section of said contour at the zone of contact of said teeth is made along the line of engagement of these teeth thereby preventing direct communication between said ports.
 2. A rotary screw-type machine according to claim 1 in which said section of said contour following said line of engagement of said teeth is adjacent to a section following the arc of the addendum circle of the teeth of said female screw on the side of said male screw.
 3. A rotary screw-type machine according to claim 1 in which one of said ports located at the high-pressure side has a contour following the line of engagement of said teeth and having a section which on the side of said male screw adjoins the section following the arc of the circle circumscribed by the radius equal to the height of the tooth of said male screw, in which case the next section of said contour on the side of said male screw is along the arc of the addendum circle of the teeth of said female screw. 